Switching mechanism



May 23, 1939. F. s- DENISON n AL SWITCHING MECHANISM Filed Jan. 2, 1937Inventors Fweefck Denison T/I/'Zlz'czm E Harrison Ernest M JJL'ZZe /wMA? farne@ Patented May 23, 1939 PATENT GFFICE SWITCHING MECHANISMFrederick S. Denison, William Ernest M. Miller, Minneapolis, Minn.,

E. Harrison, and assignors to Minneapolis-Honeywell Regulator Company.'

Minneapolis, Minn., ware a corporation of Dela- Application January 2,1937, Serial No. 118,782

22 Claims.

This invention relates to switching mechanism and more particularly tothat type of control wherein a switching mechanismactuated by acondition responsive element serves to open or 6 close a circuit or aplurality of circuits.

While this invention has particular utility in the control of an oilburner having an ignition mechanism in association therewith and. willbe hereinafter described in such connection, it is also adapted to beused with other heat producing devices in the generalart of heatcontrol.

One object of this invention is the provision of an improved connectionbetween a condition responsive element or member actuated thereby l. andcircuit controlling mechanism whereby, upon motion oi the conditionresponsive element within predetermined limits, the circuit controllingmechanism will be actuated, but upon motion in excess of such limits,the element may continue 2o to move without imparting further movementto the circuit controlling mechanism.

A further object resides in the provision oi a mechanism adapted tofunction as set forth in the preceding paragraph in conjunction with alongitudinally movable bar or rack actuated by a thermostatlc element.

A further object is the provision of improved means actuated by athermostatic element through a linearly movable rack and the connectionas above set forth to actuate a plurality of contacts, one or more ofwhich moves to open position and the others of which move to closedposition on condition change in one direction, the motion being reversedupon condition change in the opposite direction, so arranged that theclosing of certain of the contacts occurs before opening of others uponcondition change in one direction and the others close subsequent to theopening of the first mentioned contacts upon motion in the oppositedirection.

An additional object is theprovision in such a mechanism as abovementioned oi an improved means to impart a relatively rapid or snapaction to the movement of one or more of the contacts. I

A further object is the provision ot means associated with the lastmentioned means to provide a lost motion connection between the contactor contacts moved with a snap action and the member actuating the same.

lAzstill further object is the provision of an improved connectionbetween a linearly movable member actuated by a thermostatic element.and contact structure actuated thereby, the member the mechanism foractucomprising a rack and (Ul. 20D-138) ating the switch includingtoothed members cooperating with the rack.

A further object is the provision of an improved slip friction mechanismin association with the toothed members cooperating with the abovementioned rack.

An additional object is the provision ofl an improved switchingmechanism of the same general type disclosed in the co-pendingapplication of Ernest M. Miller, Serial No. '77,758 led May 4, 1936,entitled Control mechanism and assigned to the same assignee.

Other objects will in part be obvious and in part be pointed outhereinafter.

The invention accordingly consists in the features of construction,combinations of elements and arrangements of parts, all as will be morefully described hereinafter and disclosed in the accompanying drawing.

In the accompanying drawing, wherein is shown illustratively one of thevarious possible embodiments of this invention:

Figure 1 is a side elevational view of a control mechanism embodying thestructure of the instant invention.

Figure 2 is an enlarged iront elevational detail view of certainfeatures of construction embodied in the instant invention.

Figure 3 is a side elevational view` taken along the line 3 3 of Figure2 as viewed from the right.

Figure 4 is a side sectional view taken along the line 4-4 oi Figure 2as viewed from the right,

and l Figure 5 is a side sectional view taken along the line 5-5 oiFigure 3 as viewed from the left.

Similar reference characters denote similar parts throughout the severalviews of the drawing.

Referring now to Figure 1, there is generally indicated at I II a basemember to which is secured in any suitable manner a peripheral flange IIl which in turn has secured thereto an insulating panel I2 having anaperture I3 therethrough. A sleeve I4 extends outwardly through asuitable aperture I5 in member III and is secured in aperture I5 by aninwardly turned flange I6, the parts being held in related assembly inany suitable manner, as by soldering. Sleeve I4 has rigidly securedadjacent the outer end thereof a supporting member I1 which has anaperture I8 in the outer end thereof. A thermostatic element generallyindicated'at 20 which may be comprised of two substantially U-shapedsections 2i and 22,

one of which has an inwardly extending projection 23 adapted to bepassed through aperture I8 and thus held in position adjacent member I1,abuts and is secured to a rim 24. Rim 24 is in turn rigidly ailixed to alinearly movable rod 25 which extends inwardly through an aperture 26 inmember I1 and sleeve I4 through a. shield 21 positioned in sleeve I4 andis secured to an insulating block 28 in any suitable manner. A spring 29positioned between a flange 30 on insulating block 28 and shield 21serves to force block 28 and hence rod 25 inwardly in a direction awayfrom bimetallic element 20. Secured to the other end of insulating block28 as by threaded engagement therewith and held in place. as by a nut 35is a member 36 the inner extremity of which terminates in a rack 31provided with a plurality of teeth. Rack 31 passes inwardly throughaperture I3 and is associated in a manner to be hereinafter describedwith the switching mechanism generally indicated at 40 (see Figure l).It may here be pointed out that a suitable housing 4I is provided inorder that the parts of the said switching mechanism may be protectedfrom injury as well as to enhance the appearance of the mechanism.

Referring now to the switching mechanism generally indicated at 40, abracket 50 is rigidly secured as by screws 5| to insulating panel I2.Bracket 50 has an aperture 52 (see Figure 4) positioned for registrywith aperture I3. Passed transversely through suitable registeringapertures in the opposite walls of bracket 50 are a pair of axle-likemembers 54 and 55. Axle-like member 54 has mounted thereon achannel-shaped member 51 which includes a pair of substantially arcuateportions 58 having suitable apertures therein through which axle.54passes. A resilient spring member 59 is secured as by rivets 50 to theinner portion of channel-like member 51. Resilient member 59 carries at'its outer extremity a contact 6| adapted to pass through an aperture 62(see Figure 4) in channel-shaped mem.

ber 51, contact 6| being positioned for engagement with an opposedcontact 164 carried by a bracket 65 secured to insulating panel I2 as bya terminal screw 66. A suitable stop member 61 including an angularlydisposed portion 68 is positioned adjacent channel-shaped member 51 andserves as a stop to limit the motion thereof in a manner to be describedhereinafter. Positioned inside of rounded portions 58 of channel-shapedlmember 51 are a pair of friction discs 10 held in place by a pair ofopposed washers 1|, which washers in turn are rigidly secured to a pairof identical gears 12 the teeth of which are of a configuration toregister with the teeth on rack 31. A helical spring 18 surrounding axle54 fitsv into opposed recesses 19 in gears 12 and serves to urge thesame and their associated collars into frictional engagement withfriction discs 10.

Thus from the foregoing it will be seen that condition change in theregion' adjacent bimetallic element 20 is transmitted to linear movementof rod 25 and hence rack 31 and acting through gears 12 and frictiondiscs 10, serves to move channel-shaped member 51 and its associatedcontact 6| towards or away from opposed contact 64, resilient member 59serving as a strain release and likewise to provide a relativelynon-vibrating contact and friction discs 10 serving as a slip frictionmeans whereby excessive movement of rack 31 occasioned by excessivecondition change is not transmitted to movable contact 6| throughchannel-shaped member 51.

Axle 55 correspondingly carries a channelshaped member having roundedportions 8| positioned inside the walls of bracket 50. Friction discs 82are also provided as are collar members 83 secured to gears 84 similarto-gears 12. A spring 85 similar to spring 18 biases gears 82 and theirassociated collars 83 into engagement with friction discs 82 in the samemanner pre-l viously described in connection with gear 12 and frictiondiscs 10. yA cam member is rotatably positioned on a sleeve 9|surrounding spring 85 on axle 55 between gears 84. Sleeve 9| precludesthe engagement of cam member 90 with spring 85, permitting free rotationof the former. Channel-shaped member 80 carries a threaded collar 94adjacent its extremity, which collar carries a screw 95. An extendingportion 96 carried by bracket 50 has an angularly disposed portion 91provided with a threaded aperture in which is positioned a screw 98 heldin place by a lock nut 99. Screw 98 serves as a stop means for motion inone direction of channel-shaped member 80. Screw is adapted to abut asecond stop member |00 comprising an inwardly extending portion |0|extending into the pathof movement of screw 95 when moved bychannel-shaped member 80. A screw |02 secures bracket |00 to isulatingpanel I2.

Thus it will be seen that movement is imparted to channel-shaped member80 by movement of rack 31 through gears 84 and friction discs 82 in amanner similar to that discussed in connection with channel-shapedmember 51.

Referring now to cam-like member 90, as better shown in Figure 4, member90 is bifurcated at an extremity and consists of two portions |05 and|06 spaced apart a distance greater than the thickness of the upper wallof channel-shaped member 80, it here being pointed out that the upperwall of channel-shaped member 80 extends only a portion of its length asshown in Figures 3 and 4, whereby to provide a surface for alter- 1 nateengagement with members |05 and |06 of member 90. Extending in adirection towards insulating panel I2 from that portion of member 90surrounding axle 55 is a cam surface |01. Cam surface |01 is providedwith a relatively sharp shoulder |08 positioned adjacent which is aroller` |09 carried by a bracket ||0 comprising a portion of a memberIII, which is in turn secured to a resilient leaf I2 as by rivets I3,leaf I2 being secured as by rivets ||4 to a bracket ||1 carried byinsulating panel I2 which may comprise, if desired, an integral portionof bracket 50. Member I I carries a contact I I8 and resilient member I2carries a second contact ||9 which projects through an aperture inmember III. A bracket |20 secured in any desired manner to a suitableterminal carried by panel 2 in turn supports a contact |2I positionedfor engagement with contact II8. A second bracket |22 carries a contact|23 positioned for engagement with contact II9.

Thus from the foregoing it will now appear that motion is imparted tochannel-shaped member 80 by gears 84 in the manner previously describedand that such motion is imparted through the lost motion connectioncomprised of members |05 and |06 to cam member 90, screws 95 and 98limiting, as previously mentioned, the movement of channel-shaped member80.l The movement of cam member 90 is in turn transmitted through camsurface |01 to roller |09 and hence through members III and |||2 tocontacts I|8 and |I9. Thus when roller H09 passes shoulder |08 of camsurface |01 contacts |18 and ||9 move into engagement with LLI theiropposed contacts |2| and I 23 with a relatively rapid snap action.Consequently, upon reverse movement of rack 31 occasioned by a change incondition in the opposite direction roller |09 rides up shoulder |00 andthe above mentioned con-tacts are separated. It should here be noted,however, that due to the lost motion connection previously describedcontacts ||9 and ||8 engage and/or disengage their opposed contacts |2'|and |23 subsequent to the engagement and/or disengagement of contacts 6|and 64 since motion of rack 31 is immediately and directly transmittedto motion of Contact 6| whereas the lost motion connectionpreviouslyreferred to retards the immediate transmittal of such motion to contacts||8 and ||9. The utility of this arrangement will be readily appreciatedby those skilled in the art and the structure embodying such a "contactarrangement may be advantageously utilized with the system disclosed inthe previously mentioned Miller application.

It will also be' noted that axle 55 is longer than corresponding axle 54and carries, as best shown in Figures 2 and 3, on that portion thereofwhich extends beyond the wall 4of bracket 50 a cam 30. Cam |30 isprovided with an aperture I3| adapted for engagement with a projection|32 carried by channel-shaped member 00, .aperture I3|, being of greaterextent than the dimensions of projection |32 whereby to provide a lostmotion connection between projection |32 and aperture I3|. Cam |30 isprovided with a cam surface |35 having a relatively sharp shoulder |36(see Figure 3). Positioned adjacent cam surface |35 for engagementtherewith is a roller |40 carried by a bracket I4| which is in turncarried by a member |42 secured as by a rivet |43 to a resilient member|44. Resilient member |44 is in turn secured to a terminal |45 inelectrical contact as by a bridge |46 with a terminal screw |41.Terminal |45 also carries a relatively rigid member |48 which serves asa stop to limit the upward movement of resilient member |45 which isbiased by its own resiliency in a direction toward cam surface |35.Resilient member |44 carries at its end a contact |50 positioned forengagement with an opposed stationary contact |5| carriedby a bridge |52in electrical engagement with a suitable terminal |55. Thus from theforegoing it will also be seen that movement of channel-shaped memberthrough the gear and rack arrangement previously described results inthe opening and/or closing of contacts |50 and |5| with a relativelyrapid or snap action occasioned by the passage of shoulder |36 overroller |40, the lost motion connection provided by aperture I3| and |32servingto retard such opening or closing until subsequent to thecorresponding opening or closing of contacts 6| and 64. It will also bereadily understood that by suitable positioning ofcam |30 and/or cammember 90 the relative timing of the opening and/or closing of contacts|50 and |5| with respect to contacts ||8 and ||9 and their `opposedcontacts |2| and |23 may be suitably varied to provide a desiredsequence of operation in accordance with the particular installation.

The control mechanism hereinbefore described may be readily utilized forany desired purpose, but as previously mentioned its utility inconjunction with an oil burner assembly and particularly an assemblyincluding such ,a circuit as described in the previously mentionedapplication of Ernast M. Miller, will .be readily ap? preciated.

From the foregoing it will now be seen that there is herein provided astructure which accomplishes the objects of this invention and othersincluding many advantages of great practical utility.

As many possible embodiments may be made in the above structure and asmany modifications may be made in the embodiment above described, it isto be understood that all matter hereinbefore set forth or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

We claim as our invention:

1. In a switching mechanism in combination, a condi-tion responsiveelement, a rod movable thereby, teeth on said rod, a rotatable toothedmember, the teeth on said rod and said member coacting, an arm movableby said toothed memu ber, stops for said arm, a connection between saidarm and said toothed member permitting continued movement of saidtoothed member after said arm has been stopped, a first contact carriedby said arm, and a second contact positioned for engagement with saidrst contact.

2. In a switching mechanism in combination, a condition responsiveelement, a rod movable thereby, teeth on said rod, a rotatable toothedmember, the teeth on said rod and said member coacting, means movable bysaid toothed member, a yieldable connection between said means and saidtoothed member to provide a friction drive from said member to saidmeans but adapted to slip upon excess rotation of said rotatable member,a first contact carried by said means, and a second contact positionedfor engagement with said first contact.

3. In a switching mechanism in combination, a condition responsiveelement, a rod movable thereby, teeth on said rod, a rotatable toothedmember, the teeth on said rod and said member coacting, an arm movableby said toothed member, a yieldable connection between said arm and saidtoothed member, said connection comprising a friction disc interposedbetween said arm and said member to provide a friction drive from saidmember to said arm but adapted to slip upon excess rotation of saidrotatable member, means resiliently urging said arm and said member intofrictional engagement with said disc, a rst contact carried by said arm,and a second contact positioned for engagement with said first contact.

4. In a switching mechanism in combination, a condition responsiveelement, a rack movable thereby in accordance with changes in the valueof the condition to which said element responds, an axle adjacent saidrack, a pair of gears carried by said axle in mesh with said rack, achannel shaped arm mounted on said axle, the side walls thereof beingpositioned adjacent remote sides of said gears, friction discs betweensaid gears and said side walls, a spring surrounding said axle betweensaid gears and biasing the same in the direction of said friction discswhereby movement of said gears by said rack is imparted to said arm, arst contact carried by said arm, and a second contact positioned forengagement with said first contact.

5. In a switching mechanism in combination, a condition responsiveelement, a rack movable thereby in accordance with changes in the valueof the condition to which said element responds, an axle adjacent saidrack, a pair of gears carried by said axle in mesh with said rack, achannel-shaped arm mounted on said axle, the side walls thereof beingpositioned adjacent remote sides of said gears, friction discs betweensaid gears and said side walls, a spring surrounding said axle betweensaid gears and biasing the same in the direction of said friction discswhereby movement of said gears by said rack is imparted to said arm, acam movable by said arm, a movable contact adjacent said cam and movablewith a snap action thereby, and a fixed contact positioned forengagement with said movable contact.

6. In a switching mechanism in combination,

y a condition responsive element, a rack movable thereby in accordancewith changes in the value of the condition to which said elementresponds, an axle adjacent said rack, a pair of gears carried by saidaxle in mesh with said rack, a channelshaped arm mounted on said axle,the side walls thereof being positioned adjacent remote sides of saidgears, friction discs between said gears and said side walls, a springsurrounding said axle between said gears and biasing the same in thedirection of said friction discs whereby movement of said gears by saidrack is imparted to said arm, a cam movable by said arm, a lost motionconnection between said cam and said arm, a movable contact adjacentsaid cam and movable with a snap action thereby, and a xed contactpositioned for engagement with said movable contact.

7. In a device of the character described, in combination, a conditionresponsive element, a rack movable thereby, a pair of axles oppositelydisposed with vrespect to said rack, gears carried by each of said axlescooperating with said rack and rotatable thereby, arms movable by each'of said gears, and condition control means movable by each of saidarms.

8. In a device oi the character described, in combination, a conditionresponsive element, a rack movable thereby, a pair of axles oppositelydisposed withrespect to said rack, gears carried by each of said axlescooperating with-said rack and rotatable thereby, arms movable by eachof said gears, condition control means movable by one of said arms, acam carried by one of said axles and movable by one of said arms, andadditional condition control means operable by said cam.

9. In a device of the character described, in combination, a conditionresponsive element, a rack movable thereby, a pair of axles oppositelydisposed with respect to said rack, gears carried by each of said axlescooperating with said rack and rotatable thereby, arms movable by eachof said gears, condition control means movable by oneof said arms, a camcarried by the other of said arms and movable thereby, and additionalcondition control means movable by said cam.

10. In a device of the character described, in combination, a conditionresponsive element, a rack movable thereby, a pair of axles oppositelydisposed with respect to said rack, a gear carried by each of said axlescooperating with said rack and rotatable thereby, arms movable by eachof said gears, condition control'means movable by one of said arms, acam carried by the other of said arms and movable thereby, additionalcondition control means movable by said cam, and a lost motionconnection between said cam and its associated arm whereby said iirstcondition control means is operated by movement or" said rack prior tooperation of said second condition control means.

11. In a switching mechanism in combination, a condition responsiveelement, a rack movable thereby, a supporting member, an axle carried bysaid supporting member adjacent said rack, a pair of gears carried bysaid axle and meshing with said rack, a. channel-shaped member mountedon said axle, said gears being positioned between the side walls of saidmember, a recess in each of said gears, a helical spring on said axle,an end thereof seated in each of said recesses biasing said gearstowards said side walls, friction discs between each of said gears andits associated side wall, whereby a slip friction driving connection isprovided between said gears and said arm, and control mechanism operableby said arm.

12. In a switching mechanism in combination, a condition responsiveelement, a rack movable thereby, a supporting member, an axle carried bysaid supporting member adjacent said rack, a pair of gears carried bysaid axle and meshing with said rack, a channel-shaped member mounted onsaid axle, said gears being positioned between the side walls of saidmember, a recess in each of said gears, a helical spring on said axle,an end thereof seated in each of said recesses biasing said gearstowards said side walls, friction discs between each of said gears andits associated side wall, whereby a slip friction driving connection isprovided between said gears and said arm, a sleeve positioned about saidspring between said gears, a cam pivoted on said sleeve, said cam beingmovable by said arm, a Contact movable by said cam, and a xed contactpositioned for engagement with said movable contact.

13. In a switching mechanism in combination, a condition responsiveelement, a rack movable thereby, a supporting member, an axle carried bysaid supporting member adjacent said rack, a pair of gears carried bysaid axle and meshing with said rack, a channel-shaped member mounted onsaid axle, said gears being positioned between the side walls of saidmember, a recess in each of said gears, a helical spring on said axle,an end thereof seated in each of said recesses biasing said gearstowards said side walls, friction discs between each of said gears andits associated side wall, whereby a slip friction driving connection isprovided between said gears and said arm, a sleeve positioned about saidspring between said gears, a cam pivoted on said sleeve, a lost motionconnection between said channelshaped member and said cam wherebymovement of said rack is retarded in transmission to said cam, andcontrol mechanism operated by said cam.

14. In a switching mechanism in combination, a condition responsiveelement, a rack movable thereby, a supporting member, an axle carried bysaid supporting member adjacent said rack, a pair of gears carriedbysaid axle and meshing with said rack, a channel-shaped member mounted onsaid axle, said gears being positioned between the side walls of saidmember, a recess in each of said gears, a helical spring on said axle,an end thereof seated in each of said recesses biasing said gearstowards said side walls, frictiondiscs between each of said gears andits associated side wall, whereby a slip friction driving connection isprovided between said gears and said arm, a sleeve positioned about saidspring between said gears, a cam pivoted on said sleeve,

a second axle carried by said support, a second pair of gears rotatablymounted thereon, a second channel-shaped member carried by said secondaxle, a second spring biasing said second gear towards the side walls ofsaid second channel- 'shaped member, friction discs between said secondgears and said second side walls, control mechanism directly movable 'fby said second channel-shaped member, a lost motion connection betweensaid cam and said first channelshaped member, and additional controlmechanism operated by said cam whereby movement of said rack istransmitted to said cam and said additional control mechanism subsequentto transmission to said first mentioned control mechanism.

15. In a switching mechanism in combination, a. condition responsivedevice, a rod movable thereby, teeth on said rod, a pluralityfofrotatable toothed members cooperating with said rod, a control memberoperated by each of said rotatable members, and slip friction meansconnecting each rotatable member with its control member.

16. In aswitching mechanism in combination, a condition responsivedevice, a rod movable thereby, teeth on said rod, a plurality ofrotatable toothed members cooperating with said rod, a control memberoperated by each of said rotatable members, slip friction meansconnecting each rotatable member with its control member, and switchesoperated by each of said control members, said switches being operativeat different times.

17. In a switching mechanism in combination, a condition responsivedevice, a rod movable thereby, teeth on said rod, two rotatable toothedmembers cooperating with said rod for rotation thereby, a pivoted arm, aswitch operated thereby, slip friction driving means connecting said armto one oi' said rotatable members, stops for limiting the rotation ofsaid arm by said rotatable member to a relatively narrow range, a secondpivoted arm, a switch operated thereby, slip friction driving meansconnecting said second arm to the other rotatable member for rotationthereby, and stops for limiting the rotation of said second`arm to asubstantially wider range Lvllereby said switches are operated atdinerent 18. In a switching mechanism in combination'I a conditionresponsive device, a rod movable thereby, teeth on said rod, tworotatable toothed members cooperating with said rod for rotationthereby, a pivoted arm, a switch operated thereby, slip friction drivingmeans connecting said arm to one of said rotatable members, stops forlimit-- ing the rotation of 'said arm by said rotatable member to arelatively narrow range, a second pivoted arm, a pair oi switchesoperated thereby, slip friction driving means connecting said second armto the other rotatable member for rotation thereby. a cam operated bysaid second arm. another switch operated thereby, stops for limiting therotation of said second arm to a relatively wider range, and means foradjusting said stops whereby the time of operation of the switches bythe second armis varied with respect to the operation of the switch bythe nrst arm.

19. In'a switching mechanism in combination.

a. lever, a rotatably mounted cam, a stationarycontact,aswitchanncarryingamovablecontact,meansbiasingoneendofseidswitchanninto engagement with said cam. said camhaving ls.

high portion which in certain positions of said cam holds said contactsseparated against the force exerted by said biasing means, a low portionwhich permits said biasing means to close said switch contacts, and asteep slope between said two portions, a lost lmotion'connection betweensaid lever and cam so that as said cam is rotated in one direction bysaid lever said switch arm will pass from the high portion to the lowportion of said cam with a snap action, a condition responsive element,an operating member connected thereto, and slip friction driving meansbetween said member and lever.

20. In a switch mechanism in combination, a condition responsiveelement, an operating member connected thereto, a switch arm, slipfriction means connecting said switch arm to said operating member,stops for limiting movement of said switch arm, a second switch, a thirdswitch, and means connected to said operating mechanism for operatingsaid second and third switches with a snap action.

21. In a switch mechanism in combination, a condition responsiveelement, an operating member connected thereto, a switch arm, slipfriction means' connecting said switch arm to said operating member,stops for limiting said switch arm to a relatively small movement, afirst switch actuated by said switch arm, an actuating member, slipfriction means connecting said actuating f member to said operatingmember, stops for limiting said actuating member to a greater movementthan said switch arm, a second switch, a third switch, movement of saidcondition responsive element in one direction causing said switch. armto close said'rst'switch, first means actuated by said actuating memberfor opening said second switch after said first switch has been closed,and second means actuated by said actuating member for snapping saidthird switch to open position, movement of said condition. responsiveelement in the opposite direction first causing said switch arm to opensaid first switch, then causing said actuating member to actuate saidfirst means to snap said second switch closed, and saidv second means toclose said third switch.

22. In a switch mechanism in combination, a condition responsiveelement, an operating member connected thereto, a switch arm, slipfriction means connecting said switch armto said operating member, stopsfor limiting said switch arm to a relatively small movement, a firstswitch actuated bysaid switch arm, an actuating member, slip frictionmeans connecting said actuating member to saidoperating member, stopsfor limiting said actuating member to a larger movement than said switcharm, a second switch, a third switch, first and second cams connected tosaid actuating member, movement of said condition responsive element inone direction causing said switcharmtoclosesaidrstswitchandlater causingsaid actuating member to rotate said iirst and second cams to open saidsecond and third switches, movement of said condition responsive elementin the opposite direction causing said switch arm to open said nrstswitch and later causing said actuating member to rotate said first andsecond camsto close said second and third switches.

